1. Field of the Invention
The present invention relates to a system for performing communication among a plurality of electronic equipments connected with one another by means of communication control buses capable of transmitting a control signal and an information signal included therein such as a serial bus conforming to IEEE-1394 for instance (hereinafter referred to as an IEEE 1394 serial bus), and more particularly to a communication control method and electronic equipments that eliminate useless communication and also make control easier when electronic equipments control the operation of other electronic equipments.
2. Description of Related Art
A system in which a plurality of electronic equipments are connected with one another by means of communication control buses capable of transmitting a control signal and an information signal included therein such as an IEEE 1394 serial bus and the information signal and the control signal are communicated among these electronic equipments is being considered.
FIG. 9 shows an example of such a system. This system is provided with a hard disk unit 1, a personal computer 2, a television receiver (hereinafter referred to as a TV) 3, a video tape recorder (hereinafter referred to as a VTR) 4, and a set top box 5. Further, the hard disk unit 1 and the personal computer 2, the personal computer 2 and the VTR 4, the VTR 4 and the TV 3, and the VTR 4 and the set top box 5 are connected with each other by means of IEEE 1394 serial buses 6 to 9, respectively. Here, #A to #E represent node IDs on the system of the hard disk unit 1, the personal computer 2, the TV 3, the VTR 4 and the set top box 5, respectively.
Transmission of a signal in respective electronic equipments (hereinafter referred to as equipments) within the system is performed by time division multiplexing at every predetermined communication cycle (125 xcexcsec for instance) as shown in FIG. 10. The signal transmission is started when an electronic equipment called a cycle master sends out a cycle start packet showing the starting time of a communication cycle onto the bus.
The configuration of communication in one communication cycle includes two types, one being Iso communication for transmitting an information signal such as video data and audio data isochronously (hereinafter xe2x80x9cisochronousxe2x80x9d is abbreviated as xe2x80x9cIsoxe2x80x9d) and the other being Async communication for transmitting a control signal such as a control command asynchronously (hereinafter xe2x80x9casynchronousxe2x80x9d is abbreviated as xe2x80x9cAsyncxe2x80x9d). Further, an Iso communication packet is transmitted before an Async communication packet. It is possible to make a distinction among a plurality of Iso data by assigning channel numbers, 1, 2, 3, . . . , n to respective Iso communication packets. After transmission of the Iso communication packet is completed, the period until a next cycle start packet is used for transmitting the Async communication packet.
In the Async communication, a control signal used by a certain equipment when it makes a demand for something to another equipment is called a command, and the side of sending this command being included in a packet is called a controller. Further, the side of receiving the command is called a target. The target sends a packet holding a control signal showing the result of execution of a command (which is called a response) back to the controller as occasion demands.
These command and response are communicated between one controller and one target, and a series of exchanges that are started with transmission of the command and completed with sending back of the response are called command transaction. It has been decided that the target has to return a response as quickly as possible (for example, within 100 ms) after the command is received. The reason for the above is to prevent stagnation of processing when the controller side continues to wait for the response for long and processing is delayed or the response has not been returned because of some obstacle or other.
The controller can make a demand to perform specific action to the target or inquire after the present state of the target. Any equipment in the system can start and terminate the command transaction. Namely, any equipment can act either as a controller or as a target.
FIG. 11 shows a construction of an Async communication packet including a control signal. Both the command and the response have the same construction. In FIG. 11, the data of a packet are transmitted sequentially from top to bottom and left to right.
The packet is composed of a packet header and a data block. Further, standards of all of the packet headers and the data CRC in the data block, that is, the portion applied with halftone have been determined by IEEE 1394, and the contents of the data block are written from an equipment shown by source ID of the packet header to an address shown in destination offset of the equipment shown by the destination ID.
In FIG. 9 for instance, when a command is sent from the personal computer 2 to the VTR 4, the source ID, the destination ID and the destination offset are memory spaces that have been allotted as #B, #D and the area for storing the command in VTR 4, respectively. When it is desired that the personal computer 2 transmits a command to all of the other equipments in the system, 16 bits of the destination ID are set to xe2x80x9call 1xe2x80x9d. This communication configuration is called broadcast.
In the data block shown in FIG. 11, CTS (command transaction set) shows the type of command language. Further, CT/RC (command type/response code) shows the type of demand in the case of a command, and shows the type of reply to the demand in the case of a response. HA (header address) shows whether the other party for which a demand is made is the whole equipments or it is a subdevice (a functional unit) within the equipments in the case of a command, and HA is the same as the corresponding command in a sense that the other party replies in the case of a response. OPC (operation code) shows a command code, i.e., a concrete demand, and parameters required for the demand are shown with an OPR (operand) following OPC.
FIG. 12 shows a structure of a portion for making exchanges of a command and a response described above taking the VTR among the equipments within the system as an example. This VTR is provided with a VTR device 11 and an IEEE 1394 bus transmission-reception block 12.
The VTR device 11 is composed of a microcomputer, and is provided with a VTR subdevice 13 for performing processing of commands and so on related to a recording/playback system (not shown) within the VTR, a tuner subdevice 14 for performing processing of commands and so on related to a tuner (not shown) within the VTR, and a timer subdevice 15 for performing processing of commands and so on related to a timer (not shown) within the VTR. These subdevices are formed of softwares of the microcomputer.
The IEEE 1394 bus transmission-reception block 12 detects an Async communication packet received through the bus, and sends a command therein to the VTR device 11. The VTR device 11 has subdevices 13 to 15 operate, when a command is received, acceding to the concrete demand thereof. For example, when an FF (fast feed) command addressed to the VTR subdevice 13 is received, the command is delivered to the VTR subdevice 13. The VTR subdevice 13 executes processing for controlling so as to have a mechanical system of the recording/playback system within the VTR perform FF. Further, the VTR subdevice 13 monitors various status mechamode, time code or the like of the recording/playback system, and generates a response when occasion demands. This response is transmitted to the IEEE 1394 bus transmission-reception block 12 by the VTR device 11. The IEEE 1394 bus transmission-reception block 12 sends out the response to the bus being included in the Async communication packet.
FIG. 13 shows structures of formats of commands and responses and exemplifications of commands and responses with the VTR as a target. As shown in FIG. 13, xe2x80x9c0xe2x80x9dh is used here as the CTS. For example, a command demanding slow playback for the VTR subdevice 13 within the VTR shown in FIG. 12 is as shown in FIG. 13(c). The response returned against the command is as shown in FIG. 13(d). Further, the command inquiring of the VTR subdevice 13 about hour-minute-second-frame of the present value of time code becomes as shown in FIG. 13(e), and the response returned against the command becomes as shown in FIG. 13(f).
FIG. 14 shows an example of an application in which the personal computer 2 acts as a controller in the system shown in FIG. 9, and inquires about the state of all of other equipments within the system and displays it on its own display unit. This figure will be explained hereinafter.
First, when the personal computer sends a command inquiring of the TV about the input mode thereof to the TV, a response xe2x80x98VTRxe2x80x99 is returned from the TV. Next, when a command inquiring of the VTR about a mechamode of a VTR subdevice to the VTR, a response xe2x80x98STOPxe2x80x99 is returned. Then, when a command inquiring about the time code of the VTR subdevice is sent, a response of xe2x80x980 hours 25 minutes 49 seconds 24 framesxe2x80x99 is returned. Furthermore, when a command inquiring of the set top box about the reception channel is sent to the set top box, a response xe2x80x98CH6xe2x80x99 is returned.
When a command is also sent in a similar manner thereafter, and it is learnt that the mechamode, the time code of the VTR subdevice and the reception channel of the set top box have changed, display on the display unit is altered at that point of time.
FIG. 15 shows an application of xe2x80x9crewinding to the head of a tape and then playing it backxe2x80x9d as an example in which a personal computer inquires about the state of the VTR and sends a next command. Description is made with reference to FIG. 15 hereinafter.
First, when the personal computer sends a command demanding the VTR to execute REWIND, the VTR returns a response notifying of an OK on the demand and starts REWIND in the recording/playback system at the same time.
The personal computer sends a command inquiring about a mechamode or a command inquiring about the time code even after the response of an OK on REWIND has been received from the VTR. Then, the personal computer inquires again about the time code after timing is made by forecasting the time of completing REWIND, and sends further a command demanding to set the mechamode to xe2x80x98PLAYxe2x80x99 after a response showing that the mechamode is xe2x80x98STOPxe2x80x99 is returned. The VTR returns, upon receipt of the command, a response notifying of an OK on the demand, and also starts xe2x80x98PLAYxe2x80x99 in the recording/playback system.
In the applications shown in FIG. 14 and FIG. 15, they are structured so that the target returns a response only when the controller sends a command. Therefore, it is required for the controller to send the command frequently and monitor the response thereof when it is desired to confirm that the target is brought into a predetermined state.
Therefore, in case the states of equipments within the system are always displayed as the example shown in FIG. 14, or in case a series of operations are controlled sequentially in a predetermined order as shown in FIG. 15, useless communication is performed frequently as a result, and control from the controller becomes difficult. In such applications, the timing of displaying the change of the state or the timing of performing next control among a series of operations is delayed.
The present invention has been made in view of such problems, and has for its object to provide a communication control method and electronic equipments that do away with useless communication and also make control easier when the controller controls the target.
In order to solve the above-mentioned subject, a communication control method according to the present invention is characterized in that, in a system in which a plurality of electronic equipments are connected with one another by means of communication control buses capable of including a control signal and an information signal together and the information signal and the control signal are communicated among these electronic equipments, when electronic equipments control the operation of other electronic equipments using a control signal, other electronic equipments make a report on an inside predetermined state change using a control signal.
Here, another electronic equipment (a target) receives a control signal demanding start or stop of a report from an electronic equipment (a controller) on the controlling side, and starts or stops the report in accordance with the control signal. The report on the inside state change can be made either only to the electronic equipment on the controlling side or to all of the equipments within the system. This report destination can be designated by the electronic equipment on the controlling side. Furthermore, it is also possible to structure so that one type of change of an internal state designated from the electronic equipment on the controlling side is reported only once.
Further, an electronic equipment according to the present invention is an electronic equipment used in a system in which a plurality of electronic equipments are connected with one another by means of communication control buses capable of including a control signal and an information signal together and the information signal and the control signal are communicated among these electronic equipments, and comprises a first means for detecting a predetermined state change inside the equipment and a second means for sending the state change detected by the first means to the communication control bus by the control signal.
In an electronic equipment according to the present invention, it is also possible to structure so that a plurality of means for detecting a predetermined state change inside the equipment are provided, and a third means for performing centralized control of a state change detected by the plurality of means.
According to the present invention, the electronic equipment on the controlling side sends a demand either to report an inside predetermined state change or to stop the report to the electronic equipment on the controlled side. The electronic equipment on the controlled side reports, when a predetermined state change has occurred inside, the state change using a control signal. In the electronic equipment on the controlled side, a first means detects the state change and a second means sends the state change to the communication control bus by a control signal.
As described above in detail, according to the present invention, effects described in the following items (1) to (5) are produced.
(1) Since an equipment on the controlled side (a target) makes a report promptly at a point of time when a predetermined state change occurs, it becomes no longer required for an equipment on the controlling side (a controller) to transmit a command frequently in order to monitor the state of equipments on the controlled side. Accordingly, when such an application that a series of operations are controlled in order is executed, control from the equipment on the controlling side becomes easier, and useless communication becomes no longer be made.
(2) Since start and stop of a report can be controlled by an equipment on the controlling side sending a control signal demanding start or stop of the report to an equipment on the controlled side, it is possible to receive the report only when it is required. Further, it is also possible to arrange so that, not all of the equipments within the system, but a predetermined equipment only may receive the report. As a result, when a plurality of equipments exist within the system, it is possible to make the communication control bus not congested.
(3) Control from an equipment on the controlling side becomes easier by providing means for centralized control of detection of the state change inside the equipment.
(4) Communication control becomes simpler and a report on a state change can be realized without altering conventional command processing in a large way by structuring so as to report on one type of state change designated by an equipment on the controlling side only once.
(5) Realization of an application of displaying promptly upon receipt of a report on a state change or an application demanding next operation by utilizing a fact that an equipment of the other party has been brought into a predetermined state.